This invention relates to compact zoom lenses.
Recently, in the zoom lens art, a small size and compact structure has been looked for and a wide variety of proposals have been made. For example, in U.S. Pat. Application Ser. No. 770,777 (filed on Feb. 22, 1977) the power of the zoom section is distributed over three lens groups so that the amounts of movement of the lenses in the zoom section are decreased to achieve a decrease in the physical length of the entire lens system. Also, in U.S. Pat. No. 4,094,586, the decrease in the amount of movement of the zoom section is combined with a suitable design of the fixed lens group of telephoto type that follows the zoom section to effect a minimization of the size and bulk. Further, in U.S. Pat. No. 3,848,969, the bulk and size of the lens system is minimized by constructing the entire lens system from two movable lens groups.
In general, minimization of the bulk and size of a lens system may be achieved by strengthening the powers of the individual lens groups constituting that lens system. But, this gives rise to aberrational problems and, particularly the Petzval sum will be made difficult to correct. Further, the larger the zoom ratio of the zoom lens, and the smaller the intended F-number of the zoom lens then, the more difficult is the achievement of compactness of the zoom lens.